The present invention relates to a protective system for preventing damages to the tools, work, tool changing apparatus mechanisms, etc., due to any mechanical interference during the tool changing by an automatic tool changing apparatus in a numerical control machine tool such as a machining center.
There is known in the prior art an automatic tool changing apparatus which is well suited for use with machining centers, that is, an automatic tool changing apparatus which is capable of holding a large number of tools, adapted to effect the changing of tools at the nearest possible position such that the changing of the tools does not interfere with the work and capable of effecting the tool changing at a high speed. With this apparatus, a series of tool changing cyclic operations consisting of moving a tool mounted on the spindle of a head for machining a work relative to a magazine holding a large number of replacement tools to detach the tool from the socket of the spindle (lowering of the magazine), moving the arms within the magazine thereby positioning a new tool just below the socket in place of the used tool and raising the magazine thereby fitting the new tool in the socket is accomplished in several to several tens seconds. In a machining center equipped with such an automatic tool changing apparatus, however, closer the magazine is positioned to the work so as to reduce the tool changing time greater will become the danger of causing the tools and the work to interfere with each other during the tool changing, and moreover depending on the size and shape of the work the same tool changing position causes such an interference for some types of tools. As a result, there has arisen an additional problem to be solved, that is, the problem of such an interference between a tool and a work during the tool changing with the resulting damage to the tool or the work and hence to the automatic tool changing apparatus itself.